Faster boolean cross section?
You can achieve a much much faster cross section effect (almost real time) by using a simple mesh circle with a Shrinkwrap Modifier.



To set this up:


Add a mesh circle (Add > Mesh > Circle) with at least 64 verts.
Scale the circle so it's bigger than object you want to slice, and position it so that the center of the circle is at the center of your object more or less.
Add a Shrinkwrap modifier to the circle object and set the Target to the object you want to slice into cross-sections.
Set the Shrinkwrap mode to Project, and toggle both the Negative and Positive Direction on.


That's about it. You can move the circle up and down to see the cross section effect. You can hide the target object or move it to another layer to see only the cross section.

You can add depth to the circle and make it renderable by adding a Skin Modifier.

If the Shrinkwrap modifier is misbehaving, try to scale the circle or change its center position.

Here's how it looks with Skin and Subsurf modifiers added, played in real time in OpenGL: